In systems for optical navigation, frames of image data are sequentially captured and compared to track displacements of features in the frames relative to the optical navigation system. These relative displacements of the features in the frames can be used to estimate the motion of the features relative to the optical navigation system or the motion of the optical navigation system relative to the features. As an example, the relative displacements of the features can be used to track the movements of a computer mouse to control a cursor on a computer screen.
In some applications, the tracked features may be beacons (e.g., infrared sources) that are captured and used as reference points for optical navigation. The beacon sources are usually stationary, and thus, serve as reference points to determine relative motion of the optical navigation system. This type of optical navigation technique will be referred to herein as a beacon-based navigation technique. Beacon-based navigation techniques are currently used in computer gaming units to track motion of remote input devices for the gaming units.
A concern with conventional beacon-based navigation techniques is that additional hardware is needed to provide the beacons, which adds cost and undesired complexity to the overall system. Another concern is that non-beacon light sources in the field of view, e.g., candles and reflections of light, can be mistaken for the beacons, which can introduce navigation errors.
In some applications, the tracked features may be distinguishing features in a captured image frame. This type of optical navigation technique will be referred to herein as a scene-based navigation technique. Scene-based navigation techniques are similar to the navigation techniques employed in optical computer mice. Positional changes of the distinguishing features captured in successive frames of image data are used to track the motion of the optical navigation system. Scene-based navigation techniques can also be used in computer gaming units to track motion of remote input devices for the gaming units.
A concern with conventional scene-based navigation techniques is that significant navigation errors can sometimes be introduced during navigation. Such navigation errors may not be critical for applications that are not time-sensitive, such as cursor control for word processing applications. However, for time-sensitive applications, such as computer gaming, such navigation errors may not be tolerable.
Thus, there is a need for a system and method for reliably tracking an input device, such as a remote input device of a gaming unit, which does not require beacons sources.